depends on the insuarnce company. just cars are a mixed bag. they do require an aust stds immobilser as part of the policy. but I usually do alarms as they make a bit more noise than a 'stay put' device.
that said whoever does it needs to hide the thing. no point spending $2-300 on one so I can come by and remove it in 30 secs. it takes me 5-10 minutes to get at my own alarm installs...